HarmonyOS 鸿蒙Next 缓存文件至公共目录

import { BusinessError, request } from '@kit.BasicServicesKit';
import picker from '@ohos.file.picker';
import fs from '@ohos.file.fs';
import { fileIo, fileUri } from '@kit.CoreFileKit';

@Entry
@Component
struct FileCover {
  build() {
    RelativeContainer() {
      Column({ space: 5 }) {
        Button('保存').onClick(() => {
          const context = getContext(this);
          const downloadUrl = 'https://www.icbccs.com.cn/upload/829/File/201905/zhixiaodianzixieyi.pdf';
          let dirPath = context.filesDir
          let fileName = 'b.pdf'
          //防止沙箱重名导致下载失败
          if (fileIo.accessSync(`${dirPath}/${fileName}`)) {
            fileIo.rmdirSync(`${dirPath}/${fileName}`)
          }
          try {
            request.downloadFile(context, {
              enableMetered: true,
              url: downloadUrl,
              filePath: `${dirPath}/${fileName}`
            }).then((downloadTask: request.DownloadTask) => {
              downloadTask.on('fail', (err: number) => {
                console.error(`Failed to download the task. Code: ${err}`);
              });
              downloadTask.on('progress', (receivedSize: number, totalSize: number) => {
                console.log('download', "receivedSize:" + (receivedSize / 1024) + " totalSize:" + (totalSize / 1024));
              });
              downloadTask.on('complete', () => {
                //将文件复制到文件夹中
                const documentSaveOptions = new picker.DocumentSaveOptions(); // 创建文件管理器保存选项实例
                documentSaveOptions.newFileNames = ["b.pdf"]; // 保存文件名（可选）
                const documentViewPicker = new picker.DocumentViewPicker;
                documentViewPicker.save(documentSaveOptions)
                  .then(async (documentSaveResult) => {
                    // 获取到到图片或者视频文件的URI后进行文件读取等操作
                    let uri = documentSaveResult[0];
                    console.info('pub uri:' + uri)
                    console.log('保存=======' + context.filesDir)
                    // 沙箱路径文件
                    let sanFile = fs.openSync(context.filesDir + '/b.pdf', fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
                    let pubFile = fs.openSync(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
                    // 将文件从沙箱路拷贝到公共路径
                    fs.copyFileSync(sanFile.fd, pubFile.fd)
                    console.log("-------")
                  })
                console.log('下载完成')
              })
            }
              // 下载完成
            )
              .catch((err: BusinessError) => {
                console.error(`Invoke downloadTask failed, code is ${err.code}, message is ${err.message}`);
              });
          } catch (error) {
            let err: BusinessError = error as BusinessError;
            console.error(`Invoke downloadFile failed, code is ${err.code}, message is ${err.message}`);
          }
        })
      }
      .alignRules({
        center: { anchor: '__container__', align: VerticalAlign.Center },
        middle: { anchor: '__container__', align: HorizontalAlign.Center }
      })
    }
    .height('100%')
    .width('100%')
  }
}